Recovery of metals from their ores



Patented Apr. 13, 1937 RECOVERY OF METALS FROM THEIR ORES Manley L.Ross, Niagara Falls, N. Y., assignor to E. I. du Pont de Nemours &Company, Wilmington, Del., a corporation .of Delaware No Drawing.Application August 1, 1934, Serial 6 Claims.

This application relates to a process of recovering metals from theirores and more partioularly to a process in which sulfur chloride isemployed in converting the metallic constituent of the ore into a formin which the metal can be recovered. The process is of greatest utilityin recovering tungsten from its ores as tungsten trioxide.

Previously when any of the sulfur chlorides, such as. the monochlorideor dichloride or a mixture of sulfur chlorides, were employed in therecoverypf metals from their ores, it was necessary to carry out thetreatment at" a relatively high temperature and in the vapor phase. Ithas now been found that the metal present in the ore can be readilydigested by sulfur chloride and converted to a form in which it isreadily soluble at a temperature below the boiling point simply byrefluxing the ore and the extracting liquid.

The chlorides of sulfur have been used to some extent in metallurgy forconverting the metals present in the ores into chlorides and oxychlorides in which form the metallic constituent can be readilyrecovered. However, all of these prior processes have found it necessaryto employ relatively high temperatures and sulfur chloride or a mixtureof sulfur chloride and chlorine in the gaseous phase. Thus, the priorart indicates that tungsten can be recovered by passing sulfur chloridesand chlorine over a wolframite at a temperature of about 200 C. At thistemperature, by the use of the extracting medium in the gaseous phase,it has been found that substantially all the tungsten is converted to asoluble form while at the same time a'small amount is volatilized. Ingeneral, prior methods have found it necessary to work with sulfurchloride and chlorine at a temperature just under the 40 temperature atwhich the tungsten is volatilized,

which is in the neighborhood of 230 C. This relatively high temperaturehas been previously considered necessary in order to render the greaterportion of the tungsten soluble when that 45 metal is being recoveredfrom its ores.

, It is especially advantageous to convert the q carry out the reactionwithout the necessity of 7 providing pressure-resistant apparatus orwithout having to maintain a high working temperature during therecovery process.

Ithas also been necessary in the prior art where sulfur chlorides havebeen used-in ore treatment, first to ignite the ore in a furnace for twoto three hours in order to render it sufficiently soluble to permitrecovery of the metal in economically important yields. By carrying outthe step of extracting the metal from the ore in the liquid phase I havefound that this preliminary treatment is unnecessary and yields of91e92%, or higher, based upon the tungsten content of the ore, arereadily obtained without preliminary ignition. a

Throughout this description and in the claims I shall refer to thematerial used for digesting the ore as sulfur chloride although inpractice it is well recognized that one or more chlorides of sulfur maybe present in admixture. It has been found most convenient to preparethe sulfur their ores will be described using tungsten and tungsten oresas the examples. Although other metals may be recovered from their oresby the use of my process, I have found that the method is particularlysuitable for tungsten recovery ,because of the relatively high degree ofinsolubility of its oxide in the customary digestion media.

The ore to be extracted, which maybe Wolframite when tungsten is 'beingrecovered, is first ground up into small pieces. I have found thatgrinding to a fineness of 200 mesh is usually very satisfactory. The oreis next digested by refluxing with sulfur chloride and chlorine at atemperature below the boiling point, within the range 50-138 C. I havefound that a temperature within the range 125-138 C. is preferablealthough'lower temperatures, of 50 C. or higher may be employed withvery satisfactory results.

Excellent results have been obtained by utilizing about 125 parts byweight of sulfur chloride to 50 parts by weight of the Wolframite ore.The digestion may be carried out for periods of from 4 to '7 hours in anatmosphere of chlorine. The ore, sulfur chloride, and chlorine arepreferably held at the refluxing temperature for the desired period oftime (4-7 hours) and chlorineg'as may be fed slowly over the mixture. Itis not essential that chlorine be present as sulfur chloride alone iseffective; however the digestion probably prooeeds more rapidly withchlorine present with the sulfur chloride.

The yield of tungstic acid obtained by this as those of manganese andiron.

method has been found to depend upon three factors: 1) fineness ofdivision of the ore, (2) time of digestion, and (3) quantity of sulfurchloride used. The relative amounts of reagents, fineness of the ore,and digestion period given above will be found to yield verysatisfactory results.

After digestion the excess sulfur chloride in the mixtureis distilledoff and the hydrolyzable chlorides and monochlorides are hydrolyzed byboiling with water. This treatment breaks down the chlorides to aninsoluble metal compound as for example tungstic acid when tungsten isbeing recovered.

The gangue may then be filtered to free it of the acid soluble saltswhich are present as impurities and whose recovery is not desired, suchThe gangue should then be washed free of the remaining acid solublesalts, particularly the chlorides of iron and manganese, with dilutehydrochloric acid. The metal remains as an insoluble compound in thegangue.

The next step in my process is to treat the gangue with ammoniumhydroxide, aqua-ammonia. This converts the insoluble metal compound,which is tungstic acid when tungsten is being recovered, into ,anammonium salt of the metal. The extract after treatment of the ganguewith the ammonium hydroxide is then evaporated to dryness and/orignited. This treatment results in the recovery of the metal in the formof the metal oxide. When tungsten ores are being treated yields of -92%,based on the tungsten in the ore, are readily obtained.

That portion of the metal which remains in the gangue may be recoveredtherefrom by nitric acid digestion and recovered by way of the ammoniumsalt of the metal. Evaporation to dryness and ignition will yield thedesired metal oxide and by utilizing nitric acid to regain the smallamounts of metal remaining, yields of over 99%, based on the metalcontent of the ore, are not unusual when tungsten ore is being treated.

It will be readily appreciated that by digesting the ore with sulfurchloride and chlorine in the liquid phase at relatively low temperaturesa distinct improvement has been made in metal recovery methods. The useof high temperatures, and of apparatus which must be specially designedto resist high temperatures and working in the vapor phase, is no longernecessary. The yields obtained by digestion in the liquid phase are ashigh, if not higher than those which may be obtained by vapor phaserecovery methods.

As an example of mynovel process applied to the recovery of tungstenfrom its ore, numerical results illustrating two typical runs aretabulated below. As previously stated, tungsten is taken merely asillustrative and my method might be used equally as well in the recoveryof other metals.

A typical tungsten ore will analyze as follows:

Percent W03 from 73 to '75 FeO from 9 to 11 MnO from 12 to 14 CaO fromOto 1 SiOz from 0 to 1 This is a typical wolframite ore and from theanalysis it is apparent what impurities are ordinarily .present.

Example I The ore, a sample of wolframite, was ground .sulfur at l40-150C. and then condensing the efiiuent vapors. The liquid and ore wererefluxed for from 4-7 hours, the temperature being maintained below a138 C. Chlorine gas was slowly fed over the surface of the mixtureduring the digestion.

After digestion water was added to the mixture and the contents wereboiled in order to hydrolyze the remaining sulfur chloride and breakdown the chlorides and oxychlorides of tungsten present in the mixtureto tungstic acid. The gangue was next washed free of the acidsolublesalts which would otherwise be present as iron and manganese impuritiesin the product by treatment with dilute hydrochloric acid.

Sufficient ammonium hydroxide is then added to render the massammoniacal and the extract separated from the gangue by filtration. Thisextract contained the tungsten as an ammonium salt and was evaporated todryness and ignited. The yield of tungsten based on the quantity of themetal in the ore was 91-92%, the digestion period having been 7 hours.

The gangue was then treated With nitric acid in order to recover theremaining tungsten. To the extract ammonium hydroxide was added and thesolution evaporated to dryness. The total recovery of tungstic acid was97-99.6% based on the metallic content of the ore.

The following numerical values indicate the relative proportions ofreagents and amounts in two typical runs:

Run 2 Wt. of ore in grams Vol. of sulfur chloride in 00.. Time ofdigestion in hours. Wt. of W0 in ore, grams i Wt. of W0 recovered bylfur lor e trea ment, grams .1 Wt. of W0 remaining and recovered by BNO;

digestion, in grams Total W0 accnt. for, in grams yield of WO; withoutHNO; digestio W0 remaining and accnt. for by HNO;

digestion Total yield of W 0 in It is obvious that various changes mightbe made in the described method of recovering metals from their oreswithout departing from the principles herein set forth. The variousmanipulative details given in describing my preferred embodiment are tobe considered merely as illustrative and not restrictive, andvariousmodiflcations might be made therein without departing from thespirit of my invention.

I claim:

l. A process of recovering tungsten from its ores in the form oftungsten oxide which .com'- prises the steps of refluxing the ore,withsulfur chloride in the liquid phase at a temperature within therange 50 to 138 C., treating the resulting product with water tohydrolyze the tungsten compounds present in the gangue, adding aquaammonia to render the tungsten compounds soluble, filtering saidtungsten compounds from the gangue, and then evaporating the filtrate todryness to recover the tungsten.

2. A process of recoving tungsten from its ores in the form of tungstenoxide which comprises -the steps of refluxing the ore .withsulfur:chloride in the liquid phase in the presence of chicrine at atemperature of to 138 C., treating the resulting product with water tohydrolyze the tungsten compounds present in the gangue, adding aquaammonia to render the tungsten compounds soluble, filtering the tungstenfrom the gangue, evaporating the filtrate to dryness to recover thetungsten, and treating the gangue with nitric acid to recover additionaltungsten.

3. A process for recovering tungsten from its ores in the form oftungsten oxide which comprises the steps of refluxing the ore withsulfur chloride in the liquid phase in the presense of chlorine at atemperature within the range 50 to 138 C,, treating the resultingproduct with water to hydrolyze the tungsten compounds present in thegangue, washing the gangue with dilute hydrochloric acid to free it ofacid soluble salts, filtering, adding aqua ammonia to render thetungsten compounds present in the gangue soluble, filtering the tungstenfrom the gangue, evaporating the filtrate to dryness to recover thetungsten, and subsequently recovering additional tungsten by treatingthe gangue with an acid.

4. A process of recovering tungsten from its ores in the form oftungsten oxide which comprises the steps of grinding the ore into fineparticles, refluxing said ore with sulfur chloride in the liquid phasein the presence of chlorine at a temperature of 50-138 0., treating theresulting product with water to hydrolyze the tungsten compounds presentin the gangue, washing the mixture with a dilute acid to free it fromacid soluble salts, filtering, treating the gangue and tungsten mixturewith aqua ammonia in order to render the tungsten soluble, filtering,evaporating the filtrate to dryness and igniting in order to recover thetungsten as tungsten oxide, treating the gangue with nitric acid torecover any remaining tungsten, filtering,

adding aqua ammonia to the filtrate, and then evaporating to dryness toseparate the additional tungsten as tungsten oxide.

5. A process of recoveringtungsten from its ore' in the form of an oxideof tungsten which comprises the steps of refluxing the ore with sulfurchloride in the liquid phase in the preence of chlorine at a temperatureof -138 C., treating the resulting product with water to by drolyze thetungsten compounds present in the gangue, adding aqua ammonia to renderthe tungsten compounds soluble, filtering the tungsten from the gangue,evaporating the filtrate to dryness to recover the tungsten as thetungsten oxide, and then treating the gangue with an acid to recoveradditional metal.

6. A process of recovering tungsten from its ores in the form of theoxide which comprises the steps of commuting the ore, refluxing said orewith sulfur chloride in the liquid phase in the presence of chlorine for4 to 7 hours at a temperature of 125-138 C., treating the resultingproduct with water to hydrolyze the tungsten compounds present in thegangue, washing the mixture of gangue and tungsten compound with dilutehydrochloric acid in order to remove the acid soluble salts, filtering,treating said mixture of tungsten compounds and gangue with aqua ammoniain order to render the tungsten soluble, filtering the tungstencompounds from the gangue, evaporating said filtrate to dryness andigniting to recover the tungsten in the form of the oxide, treating thegangue with nitric acid to recover additional tungsten, treating saidmixture of gangue and tungsten compounds with aqua ammonia in order torender the tungsten soluble, filtering, and evaporating to dryness andigniting in order to recover the additional tungsten as the oxide.

MANLEY L. ROSS.

